Shift Timing Solenoid B Intermittent
The P078E code indicates that the transmission control module (TCM) has detected an intermittent fault in the shift timing solenoid B circuit. This solenoid controls hydraulic pressure to engage specific gears, and an intermittent signal can cause erratic shifting, delayed engagement, or slipping. The issue may stem from electrical problems, such as damaged wiring or connectors, or internal solenoid failure.
1. Symptoms You Will Notice
- Erratic or harsh shifting
- Delayed gear engagement
- Transmission slipping
- Check Engine Light illuminated
2. Most Common Causes
- Faulty shift solenoid B (intermittent internal coil failure)
- Damaged wiring in the solenoid B control circuit (chafed, cut, or corroded insulation)
- Loose, spread, corroded, or poorly retained terminals at the TCM or transmission connectors
- Intermittent short to battery voltage or ground in the harness
- Defective transmission control module (TCM) (rare)
- Low battery or unstable charging system causing voltage fluctuations
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Inspect transmission fluid level and condition.
Step 3: Visually check wiring and connectors for damage or corrosion.
Step 4: Test solenoid resistance and power/ground circuits with a multimeter.
Step 5: Perform a solenoid actuation test using a scan tool.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as intermittent shifting can lead to transmission damage. Have it diagnosed promptly.
How much does it cost to fix?▼
Repair costs typically range from $50 to $150 for solenoid replacement, plus diagnostic fees. Labor may increase total cost.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.